The invention concerns a rapid locking device for axially securing a disc-shaped tool, in particular, a grinding disc, on a flange of a driven spindle.
There are a plurality of conventional rapid locking devices for axially securing a disc-shaped tool, in particular, a grinding disc.
In conventional rapid locking devices for right angle grinders, the spindle is retained with a fork wrench or an installed spindle stop when the grinding disc is in place. An adjusting nut is then manually applied and tightened using a wrench. When the machine is switched on, the spindle rapidly starts with a jerk, and the grinding disc is automatically tightened due to the inertial mass. During subsequent working, the locking device is automatically tightened further.
In order to change the tool, the spindle is held and the adjusting nut is released using a wrench. This often requires a large amount of force.
There are also machines having a special spindle stop that can be actuated shortly before the spindle stops, and suddenly blocks the spindle. In consequence thereof, the grinding disc continues to rotate due to its inertial mass, thereby possibly releasing the adjusting nut. When the spindle stop is triggered at an excessive rotational speed, the rapidly turning grinding disc may completely unscrew the adjusting nut and the still rotating disc may be released from the spindle and cause an accident or damage. In order to counteract this, special nuts are provided which have a damping element, but which are more complex to produce than normal adjusting nuts and are more difficult to remove for changing the tool, due to increased friction.
It is however desirable to provide a braking device that stops the threaded spindle on short notice when the electric drive has been switched off. In order to reduce the risk of danger to the user by reducing the risk of contacting a grinding disc that is still turning after the motor has been switched off. Up to now, the user had to hold the angle grinder in his/her hands until the grinding disc had come to a complete standstill. When the angle grinder is put down prior to reaching a complete standstill of the grinding disc, the support surface might be damaged or a person might be injured. A plurality of developments have been made in order to prevent release of grinding discs of so-called right angle grinders having a run-out brake. DE 42 43 328 C1 discloses e.g. a design, wherein the locking element consists of a locking part which is torque-proof relative to the spindle, and a part that can be screwed onto the threaded pin, which can be turned relative to each other, wherein a device is provided between the two locking parts or between the spindle and the locking part that can be screwed onto the threaded pin, to at least partially reduce relative motion between the two locking parts. A device of this type may e.g. be an O-ring
DE 43 05 317 A1 moreover discloses a design with which a friction element is held in the adjusting nut and abuts the spindle in a friction-tight manner, in order to brake relative motion between the spindle and the adjusting nut.
DE 102 05 848 discloses a design, with which a pressure ring is provided in the nut, which can be clamped with the tool.
All above-described designs disadvantageously have relatively complex construction and the nut that projects past the tool has a relatively large axial size.
It is therefore the underlying purpose of the invention to provide an alternative solution which permits locking and adjustment of a tool, while preventing inadvertent release of the tool from the threaded spindle, e.g. during braking of the spindle.